Rechargeable lithium batteries have become widely used in both consumer and industrial applications. Rechargeable lithium batteries have a higher volumetric and gravimetric energy densities than other rechargeable batteries such as nickel metal hydride (NiMH) batteries and Ni—Cd batteries. Furthermore, the rechargeable lithium batteries have no memory effects and do not contain any poisonous metal elements such as mercury, lead, and cadmium. The applications of lithium batteries encompass a wide range of applications including small portable electronics such as notebook computers and personal digital assistants to electric vehicles and satellites.
Li(Mn0.5Ni0.5)O2 is a promising cathode material for Li-ion rechargeable batteries due to its lower cost, improved thermal safety performance, and lower toxicity compared with LiNiO2 and LiCoO2. However, Li(Mn0.5Ni0.5)O2 exhibits rather small capacity for high-energy applications and rather high impedance for high-power applications.
In addition to new types of cathode materials, various changes in the uses of lithium batteries have brought focus upon the energy density and packing density of the batteries. To achieve the high packing density of the cathode composite, spherical cathode particles with a narrow size distribution are desired. Furthermore, since a sphere has the smallest surface area among other morphology with the same volume, it is believed that thermal safety is increased with the use of spherical particles by way of reducing the contact areas between the cathode materials and liquid electrolyte.
A need therefore remains for an improved layered cathode material for use with lithium ion rechargeable batteries.